[gtk+] roundedbox: Clamp border radius to box size

[Benjamin Otte <otte src gnome org>]

commit b3f03d092fd71ba6f31a0dda20f1b00fa0d99eb3
Author: Andrea Cimitan <andrea cimitan canonical com>
Date:   Wed Jul 20 23:37:26 2011 +0200

    roundedbox: Clamp border radius to box size
    
    Note that clamping in rounded_box_grow() is not necessary as that
    function cannot lead to overlap unless the rounded box was overlapping
    previously.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=655009

 gtk/gtkroundedbox.c |   28 ++++++++++++++++++++++++++++
 1 files changed, 28 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkroundedbox.c b/gtk/gtkroundedbox.c
index 5b1eefc..c6512c1 100644
--- a/gtk/gtkroundedbox.c
+++ b/gtk/gtkroundedbox.c
@@ -48,6 +48,32 @@ _gtk_rounded_box_init_rect (GtkRoundedBox *box,
   memset (&box->border_radius, 0, sizeof (GtkCssBorderRadius));
 }
 
+/* clamp border radius, following CSS specs */
+static void
+gtk_rounded_box_clamp_border_radius (GtkRoundedBox *box)
+{
+  gdouble factor = 1.0;
+
+  /* note: division by zero leads to +INF, which is > factor, so will be ignored */
+  factor = MIN (factor, box->box.width / (box->border_radius.top_left.horizontal +
+                                          box->border_radius.top_right.horizontal));
+  factor = MIN (factor, box->box.height / (box->border_radius.top_right.vertical +
+                                           box->border_radius.bottom_right.vertical));
+  factor = MIN (factor, box->box.width / (box->border_radius.bottom_right.horizontal +
+                                          box->border_radius.bottom_left.horizontal));
+  factor = MIN (factor, box->box.height / (box->border_radius.top_left.vertical +
+                                           box->border_radius.bottom_left.vertical));
+
+  box->border_radius.top_left.horizontal *= factor;
+  box->border_radius.top_left.vertical *= factor;
+  box->border_radius.top_right.horizontal *= factor;
+  box->border_radius.top_right.vertical *= factor;
+  box->border_radius.bottom_right.horizontal *= factor;
+  box->border_radius.bottom_right.vertical *= factor;
+  box->border_radius.bottom_left.horizontal *= factor;
+  box->border_radius.bottom_left.vertical *= factor;
+}
+
 void
 _gtk_rounded_box_apply_border_radius (GtkRoundedBox    *box,
                                       GtkThemingEngine *engine,
@@ -75,6 +101,8 @@ _gtk_rounded_box_apply_border_radius (GtkRoundedBox    *box,
   if (bottom_left_radius && (junction & GTK_JUNCTION_CORNER_BOTTOMLEFT) == 0)
     box->border_radius.bottom_left = *bottom_left_radius;
 
+  gtk_rounded_box_clamp_border_radius (box);
+
   g_free (top_left_radius);
   g_free (top_right_radius);
   g_free (bottom_right_radius);